Chlorophyll-quinone photochemistry in liposomes: mechanisms of radical formation and decay

Technical Report · Tue Jan 01 04:00:00 EST 1980

DOI:https://doi.org/10.2172/6569077· OSTI ID:6569077

Hurley, J K; Tollin, G

Laser flash photolysis has been used to investigate the mechanism of formation and decay of the radical species generated by light induced electron transfer from chlorophyll a triplet to quinone in egg phosphatidyl choline bilayer vesicles. Chlorophyll triplet quenching by quinone is controlled by diffusion occurring within the bilayer membrane and reflects bilayer viscosity. Radical formation via separation of the intermediate ion pair is also inhibited by increased bilayer viscosity. Cooperativity is observed in this process due to an enhancement of radical separation by electron transfer from semiquinone anion radical to a neighboring quinone molecule. Two modes of radical decay are observed, a rapid recombination occurring within the bilayer and a much slower recombination occurring across the bilayer. The slow decay is only observed with quinones which are not tightly anchored into the bilayer, and is probably the result of electron transfer from semiquinone anion radical formed within the bilayer to a quinone molecule residing at the bilayer-water interface. With benzoquinone, approximately 60% of the radical decay occurs via the slow mode. Triplet to radical conversion efficiencies in the bilayer systems are comparable to those obtained in fluid solution (approx. 60%). However, radical recombination, at least for the slow decay mechanism, is considerably retarded.

• Research Organization: Arizona Univ., Tucson (USA)
• OSTI ID: 6569077
• Report Number(s): DOE/ER/04927-T3
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500 -- Photochemistry
550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AROMATICS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
CHEMISTRY
CHLOROPHYLL
DECAY
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELECTRON TRANSFER
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IN VITRO
LASER RADIATION
LIPOSOMES
MOLECULAR BIOLOGY
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANOIDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHOTOLYSIS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
QUINONES
RADIATIONS
RADICALS
REACTION INTERMEDIATES